This invention refers to a tropicalized petroleum sector cut-off valve gear box system and its respective method of application.
The system describes the conversion of any model petroleum sector cut-off valve gear box, into tropicalized gear boxes, in such a way as to allow its total decontamination without interruptions on the production lines, and without dismantling, making the implementation of this component proper for use in the aggressive conditions of tropical climates, so as to lengthen its service life and operational reliability.
In a country with the tropical climate and size of Brazil, the petroleum industry must build and maintain all kinds of refineries that are in strategically located areas based on their economic viability, but these locations may not always offer the best climatic conditions for operation and maintenance.
In spite of the fact that each industrial petroleum plant is built with a particular configuration and layout, all follow a standard construction concept and have common equipment.
One of these pieces of equipment is the cut-off valve. Within the diverse classifications in existence, cut-off valves may be classified as manual or remote. These valves are generally quite large and even though they may be manually or remotely activated, they have a reduction gear box that reduces force of actuation on the closing component of the valve.
For a petroleum company that holds several industrial plants, remaining competitive is an important issue, which includes questions of operational and construction costs. In this sense, much of the equipment and components are cheaper when standardized, and for this reason they adopt the use of standardized assembly, maintenance, and mainly from suppliers.
One of the great advantages large companies have is precisely that ability to negotiate with suppliers due to the large quantity and amount of standardization of the components to be acquired.
On the other hand, in a country the size of Brazil, with climates varying from equatorial to subtropical zones, containing both arid and forested regions, the components acquired will suffer the actions of the many varieties of harsh conditions caused by these climates, depending on the location of the production unit where they will be installed.
In the majority of cases involving bidding for large purchases, standardization generally represents a great saving for the company, since equipment specifications to be bought meet the technical requirements of the operation. However, a margin of error should be kept in mind as far as the harsh conditions of climate are concerned, that some equipment will suffer when installed on any unit made because harsh climate conditions may cause more equipment to be sacrificed, causing a need for more frequent changes. In these units in particular, the savings resulting from purchasing standardized products is even greater than the cost with maintenance of defects that result from severe operational conditions.
In the specific case of cut-off valves, according to studies performed on several units, the cost to equip a refinery with all the cut-off valves necessary for production start up, is equal to around 10% of the total cost of the installation of the manufacturing plant.
This study took into consideration the cost of cut-off valves supplied by large manufacturers, that in turn, due to the fact that they are suppliers of companies that by and large are located in countries with a temperate climate, choose, for reasons of cost and competitive value, the most simple and cheapest version possible for equipment, without choosing retainers, labyrinths, seals, or o-rings.
When constructed under these favorable cost conditions, some refineries located in regions with an extremely hot and humid tropical climate, need to submit their cut-off valves to a much more rigid maintenance routine than those located in a temperate climate, and even account for the down time and rectifications as a consequence of the break-down of cut-off valves.
A typical example is the situation in which the refinery located in the city of Cubatao is found. According to data supplied by the local Department of Water and Energy, it has an average annual precipitation of 2767 mm, with reports of averages above 3300 mm, which results in average values of air humidity of close to 80%, which facilitates the formation of some secondary pollutants, one of which we can cite as acid rain.
Because of the low cost of cut-off valves and the ease of negotiating with the suppliers, the national reality in regards to their maintenance is to use them until they present some type of problem. This policy is successful for the most part in refineries where these valves are installed. However in refineries located in severe climatic conditions like those in Cubatao, this policy is not possible.
The high level of relative humidity and the great shifts in temperature in short time periods, favor condensation of humidity within the gear boxes of these valves, at a level that is well above-normal. This excessive condensation results in contamination of the lubricant. Due to the loss of efficiency in lubrication, the gear box may experience several problems, from locking up of the gears, interior corrosion of the box, perforations, and even breaking of the gear box itself.
One of the solutions found by the technical corps of refineries located in these kinds of regions was to apply retainers or seals in the cut-off valves originally supplied in a manufactured unit. However this practice was shown to be impracticable because of the cost of these components, since the greater the inviolability offered by the retainer and seal models, the greater the cost of acquisition and the greater the need for techniques for installation, which makes the adoption of this solution economically unfeasible, as well as for the cut-off valves in a single refinery.
Currently these valves require a rigid maintenance plan, which consists of dismantling the entire valve. The most sensitive component of the cut-off valve is the gear box. It is completely opened, and decontaminated out of the unit, and then remounted with new lubricant.
The operation was perfected to be carried out in the least amount of time possible, since it requires that the line where the valve is installed be interrupted. This routine consumes at least 133 days to carry out the maintenance cycle on 340 cut-off valves, exposing technicians excessively in the work field. Concomitant to the maintenance work, an inspection cycle is necessary which lasts around 12 days to get to the 340 cut-off valves. If this preventative plan of maintenance and inspection are not followed it will cause unexpected down time and even possible changes of all cut-off valves, or it might require a team on duty always ready for these types of emergency situations.
The concern addressed in the development of these techniques is to try and diminish the risk of accidents, physical integrity of field operations, unscheduled interruptions to production.